The evolution of the universal mobile telecommunication system (UMTS) wideband code division multiple access (WCDMA) standards on the uplink has lagged in the past with respect to downlink transmission. The required data transmission on the downlink is usually assumed to be larger for users than the transmission in the uplink direction. It is expected that the uplink will also evolve and introduce multiple input multiple output (MIMO) technologies to reduce the peak data rate imbalance between the two link directions. Moreover, it is desirable to continue offering better service for wireless transmit/receive units (WTRUs) at the cell edge.
In order to support a higher data rate via stream multiplexing MIMO, or to support extended coverage via transmit diversity techniques, the uplink of WCDMA may be enhanced with transmit diversity techniques. Potential evolution from single transmit antenna to dual transmit antenna in the UMTS uplink may require the design of a control channel for carrying the pilot and other control information on the second or the newly added transmit antenna.